Creator's final zoom correction: as the box is dragged, its capture region slides
under the dim rectangles and the box picks up the 55% black "div shading" inside
itself, because the VisualBrush samples the whole CanvasGrid and DimRects lived
inside CanvasGrid. The captured area must stay clear regardless of box position.
- PreviewPane.xaml: the DimRects ItemsControl is now a SIBLING of CanvasGrid
(above the composed content, below the ZoomBox), never a descendant — the zoom
source is shading-free by construction.
- ZoomBoxInteractionTests: structural invariant — DimRectsLayer is a direct
child of PreviewCanvas (not inside CanvasGrid) and renders below the ZoomBox.
- Side effect (correctness, not a bug): quality dims now also sedate the global
overlays outside the crop, matching "chrome outside the crop is dimmed".